One of the most recognizable buildings on Post Office Square is getting a new look. The owners of 50 P.O. Square, the massive Art Deco structure that long housed New England Telephone & Telegraph, are building a new lobby on High Street, with a 35-foot-high glass curtain and an indoor-outdoor LED board designed to highlight the way people move through the lobby and the street outside.

It’s the latest lobby in the neighborhood to get a re-do. Across the street at 100 Federal, developers are erecting a huge glass atrium on the sidewalk, while other buildings around Post Office Square are in line for lobby upgrades, as the Financial District faces more competition from the Seaport.

Owners LaSalle Investment Management say they hope to create a “building within a building” with the lobby, which will give access to the first six floors, and a new roof deck. Construction is underway and will finish this summer.